“My Cross-Border PhD Journey”: A Qualitative Study on the Educational and Life Challenges of Mainland Chinese PhD Students in Hong Kong

PhD students’ poor mental health has been increasingly concerning. However, challenges among PhD students studying aboard are understudied. The Educational and Life Transitions (ELT) model postulates that international PhD students are subject to both academic and acculturative stressors; however, relevant research is limited in the Chinese context. We examined mainland Chinese PhD students’ study and living experiences in Hong Kong using a qualitative approach. Through purposive sampling, 37 mainland Chinese PhD students in different disciplines from public-funded universities in Hong Kong were recruited to participate in online focus group interviews (December 2020–February 2021). The interviews were analyzed using the framework analysis method. Ten themes of academic/acculturative stressors were identified. The academic stressors included: (1) high expectations from the supervisors; (2) emphasis on self-discipline as PhD students; (3) peer comparison in academia; (4) difficulties shifting research directions/academic disciplines; (5) uncertainties about future career. The acculturative stressors included: (1) differences in the political environment; (2) language barriers; (3) difficulties living in Hong Kong; (4) limited social interaction with others; (5) local people’s discriminatory behaviors. This study sheds light on the stressors experienced by mainland Chinese PhD students in Hong Kong. To better address those students’ academic and acculturative stressors, cross-cultural training and additional support from supervisors/the university could be provided.


Introduction
At present, there is a mental health crisis in academia [1]. According to the latest Nature's global survey of graduate students in 2022, which included 3253 graduates from six continents (87% came from Europe, North America and Asia), over one-third of PhD respondents report that they have received help for anxiety or depression caused by their study [2]. This rate is far higher than the 12% found in Nature's global survey in 2017 [3], which calls for urgent attention to the mental health of PhD students.
"Doctoral researchers are a key part of universities, they're future thinkers, innovators and leaders that are vital in building and sustaining our economy", as said by Professor Jeremy E. Niven, Dean of the Doctoral School at the University of Sussex, who led a nationwide study of the mental health of UK doctoral researchers [4]. As a result of this importance, concerns for PhD students' well-being have been growing in academic research. Studies from Australia, Belgium and the U.S. showed that PhD students experienced a greater incidence of mental illness than the general population [5][6][7]; their mental health risk was also higher than that of master's students in the higher education field [8]. Meanwhile, evidence from three systematic reviews suggested that PhD students studying in their home countries (e.g., U.S., U.K., Canada, Australia, Finland, Netherlands, China, Malaysia) are at risk of poor psychological well-being [8][9][10]. We could expect that PhD students studying overseas might suffer more due to the exposure to other aspects of stressors as sojourners.
According to the Educational and Life Transitions (ELT) model [11], international doctoral students not only need to go through transitions in a new educational system, but also face challenges living in a new society. The ELT model clearly differentiates international university students from other cross-cultural sojourners, such as business expatriates and short-term exchange students [12]. It incorporates a holistic look into the analysis of adaptation to daily and academic life among international university students [13].
Although the ELT model is designed for international doctoral students, relevant research on the PhD population is scarce. In addition, most of the previous empirical research only investigated one type of transition in the ELT model, while the double transitions were not valued equally in these studies. Adopting the transition concept pointed out by the ELT model, Pho and Schartner [14] used a mixed-methods approach to explore the social contact patterns of 101 international students undertaking taught postgraduate degrees in the U.K., and examined its relationship with academic achievement and adaptation. The findings suggested that social contact is an important contributory factor for academic adaptation and that more contact with other non-co-national international students provided important emotional and academic support. Najjar [15] conducted interviews among 34 international doctoral students from a midwestern research institution in the U.S. to investigate their advising relationships and adaptation experiences. The findings revealed specific obstacles related to language difficulties and interaction within/outside the academic environment, immigration or visas and family and financial concerns (personal incomes and academic financing). Byrne, et al. [16] adopted the focus group interview design among 31 international medical students in an Irish university to explore their challenges in social adaptation and interactions. The findings revealed the positive and negative aspects of daily-life transition and highlighted that making friends, as well as cross-cultural communication, were the main challenges facing international medical students. McGarvey, et al. [17] conducted focus group interviews among 31 international medical students in their senior clinical years in a medical university located in Ireland to explore the impact of the participants' cultural backgrounds and language on their transition as international medical students to the clinical years of their training. The findings pointed out the daily life challenges (e.g., cultural integration and poor transportation) and academic challenges (e.g., language, practice religious belief) among these senior international medical students.
PhD students are subject to a spectrum of academic stressors throughout the PhD journey; for example, time pressure for work-life balance and worries about delayed graduation, uncertainty of the PhD process (i.e., finding a clear research direction independently, the ambiguity of completing a doctorate, uncertain career prospects), financial concerns and their supervisory relationship [18][19][20]. Meanwhile, international students often have many difficulties when moving to a foreign country to study, such as language barriers, loneliness, discrimination and practical problems associated with changing environments [21]. Thus, they may experience acculturative stress (i.e., psychological stress resulting from the acculturation process [22]) and may have social, psychological and behavioral changes [23].
The intensity of acculturative stress is strongly influenced by the similarities or dissimilarities between the host culture and that of the new entrants. The more differences between the host culture and the newcomer's native cultures, the more acculturative stress will be experienced [24]. Therefore, it is plain to see that Chinese international students in America, Europe, Oceania or other western countries are more likely to suffer from culture shock or adaptative problems [15,25,26]. However, in some Asian countries (e.g., Korea, Japan, Singapore, Malaysia), although there may be more similarities with the Chinese culture, Chinese international students also report having experienced acculturative stress and adjustment challenges [27][28][29][30][31]. Noteworthily, research has shown that people moving to another region within the same country (i.e., internal migration) may also encounter 'culture shock', parallel to international migration [32]. In the Chinese context, emerging studies have examined internal migration (mainly rural-to-urban) and health among children, adolescents [33,34] and migrant workers [35,36] in China; however, students who migrate for pursuing higher education are usually ignored.
Due to special historical reasons (i.e., Hong Kong was a colony and later a dependent territory of the British Empire from 1841 to 1997), Hong Kong has been influenced by both Eastern culture and Western culture. This unique cultural environment attracts many mainland students coming to Hong Kong for pursuing higher education. The data suggest that research postgraduate (RPg) students recruited from mainland China occupied 67.3% of the total RPg students (n = 7602) in Hong Kong in 2017-2018, which is a 15.59% increase from 2007-2008 [37]. These mainland PhD students constitute the largest group of nonlocal students in Hong Kong. However, even though Hong Kong is a place with higher geographical proximity and cultural similarity with mainland China than other countries, it is still common for these mainland Chinese students to encounter difficulties while studying and living in Hong Kong. Some of them 'feel lonely and stressed', 'encounter language barriers', 'feel discrimination', 'experience cultural differences' and 'feel difficult to integrate into local life' [38][39][40]. Specifically, mainland students meet language barriers when adapting themselves to a bi-lingual environment (English for academic purposes and Cantonese for social interaction [41]) when studying in Hong Kong [38]. Cultural differences refer to the subtle difference between a subculture (Hong Kong) and its mother culture (Mainland China), such as the social norm, living style [40], as well as differences in the academic cultural environments [42]. Mainland students also have limited social network/interaction, and even suffer from social isolation or social exclusion [43,44]. Although prior studies have focused on mainland Chinese undergraduate or master's students in Hong Kong, studies specifically on PhD students are limited; we can still expect that mainland Chinese PhD students in Hong Kong may also experience difficult times in their educational and life transitions.
Studies on the dual levels of challenges (academic and acculturative) among mainland Chinese PhD students' adaptation in the intranational settings are limited [45]. Most of the research investigating Chinese international PhD students has focused on academic adjustment and was conducted in a particular foreign country outside of China. For instance, Hu and Zhao [46] explored the interactions between Chinese doctoral students and their supervisors at Dutch universities, using the interviews approach, to reveal the challenges in fostering independence in such an intercultural context. Wang and Räihä [47] used the case-study approach to explore how Chinese doctoral students integrate into the Finnish learning environment. Zhang [48] explored the transition experiences of international Chinese doctoral students at a U.S. research university. Furthermore, no local study to date has specifically examined the educational and life transitions among mainland Chinese PhD students in the context of within-country migration. Therefore, to fill in this research gap, and guided by the ELT model, this study aimed to examine mainland Chinese PhD students' study and living experiences in Hong Kong using a qualitative approach.

Methods
This study used focus group interviews for obtaining qualitative data from the participants. Compared to individual interviews, focus group interviews can obtain information about the similarities and differences in people's perspectives in a group setting, as well as generating large amounts of data in a relatively short time [49]. Focus group interviews have been commonly used in qualitative/mixed-method studies exploring international students' acculturative and academic experiences [40,[50][51][52].

Recruitment
Eligible participants of this qualitative study were: (1) full-time mainland Chinese PhD students enrolled in one of eight publicly funded universities in Hong Kong; (2) aged ≥18; (3) holding a student visa issued by the Hong Kong immigration department; (4) having been studying in Hong Kong for at least 6 months (to ensure they had some experience adjusting into the local society and academic studies); (5) Mandarin-speaking.
Prospective participants were recruited with purposive sampling through multiple channels. For example, the electronic study announcement of this study was posted through the postgraduate students' mass e-mail system. Similar to a previous study [53], we collaborated with the Chinese Students and Scholars Association (CSSA) of the eight publicly-funded universities in Hong Kong to distribute the study flyer on their WeChat official accounts of those associations and alumni's WeChat groups. Regardless of the recruitment channels, the study flyer described the purpose, eligibility criteria and procedure. A web link and QR code, which was generated on an online survey platform (Tencent Questionnaire), were embedded at the end of the study flyer. The study was conducted from December 2020 to February 2021.

Preparation of Interview Outline
A semi-structured, open-ended interview protocol was prepared for this study. Guided by the ELT Model [11], acculturation experience and academic experience were derived as priori themes in the interview outline. The interview questions were developed with reference to other relevant studies on mainland students' adjustment in Hong Kong [40,54] and international doctoral students' academic and adaptation experiences [15,55].
The interview protocol was pilot tested among 6 postgraduate students from mainland China who major in public health to ensure the questions were relevant to the target population's experiences. After obtaining feedback from the pilot interviews, the questions were reviewed and discussed again among the authors for the finalization of the interview protocol. The interview questions are listed in Supplementary Materials Table S1.
Interested participants were invited to register for the study by contacting the first author individually or filling in the registration form attached to the study flyer. After checking eligibility and obtaining online informed consent, 6-8 interviewees were assigned to each group based on their characteristics (e.g., institutions, academic disciplines, stage in the PhD journey) and preferred interview time. Each focus group interview was scheduled on the weekend.
Participants were recommended to participate in the interviews in a quiet room with proper lighting and to check the stability of their Internet network. A reminder e-mail with detailed interview information (e.g., login information for the online focus groups) was sent to participants.
Considering the COVID-19 pandemic situation and social distancing measures in Hong Kong, the online focus group interviews were conducted and recorded via Zoom. The first author served as the moderator, conducting the interviews and facilitating the focus group process. As suggested by Millward [56], the direct involvement of the researcher is useful because of their rigor in methodology and sensitivity to the issues. The focus group interviews were conducted in Putonghua, the native language of the target population and the focus group moderator. Participants were asked to turn on their cameras until the end and were reminded that the interviews were audio-recorded. The participants could use nicknames/alias during the interview. Each interview lasted around 90 min. Participants who finished the focus group interviews were given RMB 50 through WeChat pay or Alipay as compensation for their time. This qualitative study has been approved by the Survey and Behavioral Research Ethics Committee at the authors' institution (Reference No. SBRE-19-575).

Data Management and Analysis
The audio recordings of the interviews were translated using Notta (a professional audio-to-text transcribing software). The interviews were then reviewed by the first author and double-checked by another trained coder (a mainland PhD student from Social Science, with a linguistics degree). Microsoft Word (embedded with DocTools, with a function to extract and export text from Word to other platforms) and Microsoft Excel were used for extracting and coding the qualitative data. Specifically, the audio files were transcribed verbatim to text, the text was transferred from Word to Excel and coded in Excel, then the coded interviews were sorted by the relevance of the codes and the quotes and references were transferred from Excel to Word; then, the texts were sorted into a logical structure (i.e., priori themes) based on the coding and, finally, analyzed by two coders individually [57]. Framework analysis was used to guide the coding and analysis process of the qualitative data, which consists of five key stages: familiarization, identifying a thematic framework, indexing, charting, mapping and interpretation [58]. Guided by the ELT model, academic stressors and acculturative stressors were classified as "a priori" themes [59] before identifying the matric framework.
To guarantee the trustworthiness of the data and reduce bias, two coders (the first author and the trained student) coded the transcripts independently [60,61]. The two coders reviewed the codes and classified them into themes and subthemes. When discrepancies in the codes emerged, the coders discussed and resolved them to reach a consensus. Inter-Rater Reliability (IRR) was used to measure the extent to which the different researchers agreed on how to code the same content [62]. Researchers are suggested to calculate both the percent agreement and Cohen's kappa to reduce the limitations of both IRR measurements [63]. Specifically, percent agreement = number of agreements/(number of agreements + disagreements) [64] and an 80% agreement between coders on 95% of the codes is sufficient agreement among multiple coders. Cohen's kappa = (actual observed agreement − chance agreement)/(1 − chance agreement) and 0.81-1.00 represents perfect agreement between the raters [63]. After the calculation, the percent agreement was 95.1% among all the codes and the Cohen's kappa was 0.9; both indicated a very good agreement between the two coders in this study.

Sample Size Planning
Factors determining the sample size in qualitative studies include the topic, data quality and study design. The number of participants to be recruited was determined by data saturation [65]. Based on previous studies on the acculturation experiences of mainland Chinese students in Hong Kong [38,40], data saturation is generally achievable with a sample size of 32. For each group interview, 6-8 participants are recommended to show the greatest potential of the group discussion and information saturation [66]. Among 42 prospective participants expressing interest in this study, 37 were eligible.

Themes
Guided by the ELT model, ten subthemes from the two major aspects of stressors (academic stressors/acculturative stressors) were derived from the focus group interviews. A summary of the themes and subthemes is presented in Supplementary Materials Table S2 and Figure S1.

Theme 1: Academic Stressors
Most of the participants believed that their academic journey was stressful. Their stressors consisted of high expectations from the supervisors, emphasis on self-discipline as PhD students, peer comparison in academia, difficulties shifting research directions/ academic disciplines and uncertainties about their future career ( Table 2). The participants' academic stressors seemed to vary across their disciplines; with or without relevant research experience, the quality of the supervisory relationship also makes a difference. Uncertainties about future career 5 5

High expectations from the supervisors
The participants agreed that the supervisor plays a vital role in the academic journey, and many reflected on their tendency to follow the supervisor's guidance and expectations. High expectations from supervisors usually pose a challenge to the students. In addition to the program requirement, supervisors usually have requirements about the quantity and quality of publications, especially for students from the Science faculty. Students from the Arts or Social Science faculties experienced less pressure to publish, which might reflect some differences in PhD education across disciplines.
Patrick: "My supervisor likes to do pioneer work and make outstanding contributions to one field; instead of repeating what someone else has already done, he hopes us do that kind of challenging thing, but it will be quite difficult at the beginning for us students." Kaylee: "My supervisor has a very clear expectation on the students' publication, she asks me to publish five to six papers, expects me not just to meet the minimum requirements (set by the program), she also set a higher standard." However, some students believed that their supervisors did not provide them with adequate guidance. For example, some supervisors only showed little concern or provided little guidance (due to lacking relevant expertise) to students' research, which increased students' difficulties to progress, or even delayed their graduation.
Xing: "My research requires me to do experiments, my supervisor is good at doing modeling but completely not skilled in doing experiments . . . I found it quite difficult, which was equivalent to starting from zero, roughly." CY: "There is no guidance on my thesis project . . . delay graduation is a common phenomenon in our faculty, no student guided by our supervisor could graduate on time."

2.
Emphasis on self-discipline as PhD students Many participants found that conducting research as PhD students strongly emphasizes self-discipline and independence. PhD education is regarded as a journey that requires a high level of independence and skills to manage one's time and research-related problems. Students need to make good use of the limited time and deal with problems they encountered to graduate in a reasonable timeframe.
Stacey: "PhD study requires us to have a strong ability to be self-managed." John: "Everyone is very independent in their work, and there is no one to discuss with except the supervisor. Moreover, when you have problems, you cannot always ask the supervisor to answer you. And then you may get stuck in one thing that you don't know what to do, that's the hardest part." Panda: "Unlike previous study or work, I have a clear task list and timeline to finish every day; I feel more stressed in the doctoral study is that I often don't know how long to finish one task (I often can't comply with my schedule). Also, PhD study requires me to have a higher level of time management or the ability of self-control."

3.
Peer comparison in academia Peer comparison in academia was commonly mentioned by the participants. Those students might compare their performances with previous college classmates, PhD classmates enrolled in the same year, PhD students guided by the same supervisor and other PhD graduates with the same major from different universities. For newly enrolled PhD students, it was common for them to compare themselves with previous college classmates. However, senior PhD students usually compare themselves with other fellow PhD students within the same institution and outside their institutions. For example, some students try to keep pace with previous students to attain the same quantity, or more, publications, while others felt worried about the need to compete with other PhD candidates/graduates in the job market.
BF: "At the first 2-3 months after enrollment, when I was busy reading literature to propose a research topic, they (my former classmates studying for master's degree in mainland China) have already started doing experiments and some even start writing paper, which brings me a great of stress." Laura: "Your various performances in PhD will be assessed, and that is, taking various courses, especially statistics classes. I am under great pressure to complete my project, especially when my colleagues around me work hard and excellent." Naruto: "My supervisor expects students to publish four or five papers in top journals within four years, and the former PhD students guided by my supervisor usually publish six papers before graduation. So, you must have a paper every seven or eight months, I feel bigger stress." Jianing: "You need to catch up with the speed of people competing with you, you need to publish more papers and faster than others, then you have chance to land that (job) position."

4.
Difficulties shifting research directions/academic disciplines Some participants mentioned that their PhD major is different from their major at the undergraduate/master's levels. Exploring a new field can be puzzling and hard. In contrast to undergraduate or graduate education, in which the University provides a series of classes to help students grasp the core knowledge and skills, PhD education also expects students to possess critical thinking skills and original research ideas. For the students who change their major or research direction, setting aside what they were knowledgeable about and restarting to explore a new area were challenging.

5.
Uncertainties about future career PhD education could be an important steppingstone for one's academic career. Compared with junior PhD students, senior PhD students are more concerned about their career development. Students who planned to work as research staff in colleges or institutions after graduation were also worried about the difficulties of attaining a decent job position. The increasingly stringent job recruitment criteria (i.e., in terms of the quantity and quality of publications) exacerbated the students' stress.
Jianing: "China's current situation (in academia) is like a rising tide lifts all boats (" 水 涨船高" in Chinese, in our context it means the universities' recruitment criteria for limited job positions become higher and stricter when more PhD graduates influx into the supply market), and then it's involution (" 内卷" in Chinese, in our context it means excessive competition in the academia, causing over qualification and evaluation pressure among PhD graduates)." Naruto: "My supervisor hopes I can publish more articles, which is also want I intend to. Most PhD students want to find a teaching position in the future. If you don't have enough publications, it will be difficult." Pursuing a PhD is very time-and resource-intensive, with so much effort from the university, faculty and students. Even with those efforts, Some PhD students were still uncertain about their future career path; others did not want to find a job in academia.

Theme 2: Acculturative Stressors
In addition to academic stressors, the participants experienced difficulties adapting the life in Hong Kong. Their acculturative stressors included differences in the political environment, language barriers, difficulties living in Hong Kong, limited social interaction with others and local people's discriminatory behaviors (Table 3). It is noteworthy that their acculturative stressors seemed to vary across different geographical regions of their hometowns. Participants from northern and western China experienced more difficulties in understanding and speaking Cantonese, in addition to adjusting to the local climate and food choices.

Differences in the political environment
Hong Kong is strongly influenced by both Western and Chinese cultures, potentially due to the prior occupancy by the British for 156 years. After the handover to China in 1997, Hong Kong maintained autonomy in the governing and economic systems from those of mainland China under the principle of "one country, two systems". The participants perceived the differences in the political environment and beliefs between Hong Kong and China, which brought them a great deal of stress. We found that political issues were regarded as sensitive topics that mainland students usually avoided talking about. Such perceptions could affect how they select research supervisors, make friends and communicate with local people in daily life. To those participants, local people were highly involved in political activities. Many of the participants could not tolerate politically related violent behaviors (the participants mentioned some events that happened in 2019 during the social movement in Hong Kong). Those events brought them trauma-like psychological symptoms.

7.
Language barriers As one of the participants (Willa) said, "Language is an important part of adapting to the local environment." Cantonese is the first language in Hong Kong. Being a district dialect in mainland China, Cantonese is also the first language in southern China, particularly in the Guangdong province, which is geographically adjacent to Hong Kong. Compared to students from the Guangdong province or neighboring provinces, it is not surprising to note that participants from northern and western China experienced more difficulties in understanding and speaking Cantonese. One participant from the Fujian province (Lyman) said "it (Cantonese) sounds a little bit like my hometown dialect." Even though participants from the Guangdong province did not experience difficulty in understanding and speaking in Cantonese, they also noted some subtle differences in the slang and expressions of the local people. It is also interesting to learn whether the participants perceived language as a barrier depending on how much they practically need to use it in daily life. Some students did not perceive a language barrier as they did not see a lot of need to interact with local people. Other students felt that their Cantonese proficiency improved as they stayed in Hong Kong longer.

Difficulties living in Hong Kong
The difficulties of living (accommodation, climate, and food) in Hong Kong also affect the participants' adjustment to local life. Participants from northern China experienced more difficulties in adjusting to the climate and food in Hong Kong. To most of the participants, the accommodation was not spacious in Hong Kong. As they stayed longer in Hong Kong, they became used to the local residential environment and living conditions.

9.
Limited social interactions with others Many participants mentioned that their social interactions with people outside the academic settings were quite limited, regardless of this being with mainland students or local people. As one participant (PY) said, the 'sense of boundary' of people around made it hard to make friends. In most cases, mainland PhD students tended to develop social networks in the same workplace or same student hall. Physical proximity facilitated those students' social interaction.
Bean: "It is difficult to make friends after I came here. Especially hard to make close friends."

PY: "Local people have a strong sense of boundaries with other people. In fact, it is not only among local students but also many mainland students in Hong Kong. I don't know if they are assimilated into the environment of Hong Kong, if they change the way to interact with people after coming to Hong Kong, or if they behave in accordance with the characteristics of Hong Kong, probably the last reason."
The other factor affecting students' social interaction was being occupied by their busy PhD study. Many participants mentioned that their academic workload occupied most of their time. To avoid unnecessary distractions, they were not motivated to make more local friends. Chen

Local people's discriminatory behaviors
A few participants shared their experiences of being discriminated against (both on and off campus). These participants experienced being treated unfairly because they spoke Mandarin or came from the mainland. Some local people treated them in an unfriendly way and felt that they were superior to the mainland people. The participants expressed their fear, discomfort and disappointment when talking about such experiences.
Alice: "In 2019 (social movement) I don't dare to speak Mandarin and I'm afraid there will be some people discriminating against me. Because there is a rumor that someone speaks Mandarin and then gets sprayed with paint on the subway." Willa: "I used to study at a university that has a lot of Hong Kong students in the mainland, at that time I can obviously feel their so-called superiority. And then after coming to Hong Kong, I always have such feelings. It's not only about the language, and local people's sense of superiority will make it more difficult to integrate into the society." Chen: "When I come to Hong Kong, I would like to make these local friends, but they can naturally distinguish you (mainland people) from local people. Just because of the different identity, they don't understand you, put labels on you, and wear color class (" 戴有色眼镜" in Chinese, in our context it means having prejudice and looking down at someone) to see you. These behaviors made me can't communicate with them anymore."

Theme 1: Academic Stressors
This study identified several important aspects of academic stressors among mainland Chinese PhD students in Hong Kong, including high expectations from the supervisors, emphasis on self-discipline as PhD students, peer comparison in academia, difficulties shifting research directions/academic disciplines and uncertainties about future careers. The findings were largely consistent with previous studies conducted in Western countries (e.g., the U.K., New Zealand) [18,19] and mainland China [67].

High Expectations from the Supervisors
Similar to Wang and colleagues' qualitative study among ten PhD students in mainland China [67], our participants reported distress about the lack of guidance on research. In both cases, supervisors were absent from their responsibilities, showed no interest or feedback on students' research and did not give adequate support to the students. When proper equity and protection for students are in shortage in the supervisory relationship, it seems easier for those from East Asian universities (e.g., China, Korea, Japan) to accept this supervisor-centered, hierarchical relationship as they are more likely to endorse traditional Confucian values [68,69]. However, this phenomenon is unusual in European universities (e.g., German, Finland, Luxembourg) [70,71]. Culture may be a significant factor that affects the supervisory relationship in the academic environment.
There is also one special case-that is, when the student's research is out of the supervisor's expertise, such as conducting experiments or modeling-reflected by our participants; this is not a matter of responsibility, but rather, competence. We will discuss this situation in the following paragraph (difficulties shifting research directions/ academic disciplines).
We highlight that supervisors' expectations of academic publications also bring an additional stressor to the students. This finding was consistent with a prior study among 30 Chinese doctoral supervisors in different natural and social science disciplines [72]. Supervisors may pass their performance-appraisal-related stress to students. The standard for the quantity or quality of academic publications is likely to originate from the supervisor's pressure to pursue the sustainability of their career path, such as attaining a higher level of academic position or obtaining a scientific foundation/grant. However, given that the participants did not specifically mention whether journal publications were prerequisites for their graduation, we could not rule out the possibility that those expectations for publication also come from the program requirements.

Emphasis on Self-Discipline as PhD Students
Our finding was in line with previous studies conducted among Chinese international PhD students overseas (e.g., Australia, Finland, Malaysia) [47,73,74]. Meanwhile, our findings among junior PhD students and senior PhD candidates were also consistent with those reported by overseas PhD students. In particular, isolation brought about by owning a research topic and pursuing it alone [19], both intellectually and socially, poses challenges to students' self-discipline, independence and time-management skills. Early-stage doctoral students tended to report pressure on proposing research questions and work-life balance [18], while late-stage PhD candidates were prone to report pressure on managing research progress, developing domain-specific expertise and meeting the requirements for graduation [20]. Moreover, as an individual characteristic, self-discipline is found to predict academic procrastination among international graduate students [75]. In this sense, it may be worthwhile to further explore the connection between students' personal traits and their PhD experience.

Peer Comparison in Academia
Peer comparison seems to be a commonly experienced stressor by our participants, especially for those majoring in science disciplines. It has been a trend that Chinese universities increasingly use the number of international publications as a major assessment and incentive measurement of their faculties' academic performance, such as in the science and engineering disciplines [76]. As a result, the pressure for academic publication transfers to the recruitment process, which brings anxiety to the PhD candidates who aim to find a job in the academic field.
This does not only happen in China; Haven and colleagues [77] conducted a survey of all disciplinary fields and academic ranks among 1073 researchers in Amsterdam to explore their perceived publication pressure. The results showed that researchers in the humanities perceive greater publication stress than both biomedicine and the natural sciences. PhD students, especially PhD candidates, perceived a significant lack of resources to relieve publication stress. In our study, however, due to our study design, we could not compare the level of publication pressure; the limited number of participants from humanity disciplines also confine our findings.

Difficulties Shifting Research Directions/Academic Disciplines
In contrast to prior findings, our participants highlighted the difficulties in changing discipline or research direction as another transition stressor. Many participants (primarily those in science majors) indicated that their research topic/direction did cater for interdisciplinary research needs. As indicated by Golde and colleagues [78], for students who need to conduct interdisciplinary research, finding a supportive advisor and a proper community, mastering knowledge and reconciling conflicting methodologies and overcoming fear were their major challenges. Those students were likely to experience stress due to their lack of qualifications and specialized training in the multiple disciplines needed for their research [79]. For early-stage doctoral students, changing discipline or research direction usually brings frustration and reduces the sense of belonging to a research group [80]. However, they tended to normalize that as a part of the "difficult" PhD journey.

Uncertainties about Future Career
Consistent with PhD students in mainland China [67], many of our participants shared their plans to return to mainland China for seeking jobs as they worried about the limited job opportunities in the local market and the fierce competition with other scholars. Similar phenomena were also apparent in doctoral candidates, based on a scoping review of 26 studies conducted in Western countries [20].
It should be noted that most of our participants were year 2 and year 3 PhD students. They did not express urgent worries about their career path compared with senior PhD candidates. It is also noteworthy that all of our participants were not provided with any training/workshops specifically targeted to their career development. It would be important to explore whether those workshops could facilitate planning for their future career.

Financial Concern Is Not a Stressor
In contrast to many PhD students studying in Western countries that deemed financial insecurity as the largest stressor [20], none of our participants reported financial pressures. A steady and secure financial income is a decisive factor for Chinese international doctoral students choosing to study abroad [81]. As Hong Kong's publicly-funded universities offer PhD studentship stipends to their PhD students [82], it is possible that most of the full-time mainland PhD students have sufficient financial support for their research needs and living expenses.

Theme 2: Acculturative Stressors
This study identified several important aspects of acculturative stressors among mainland Chinese PhD students in Hong Kong, including differences in the political environment, language barriers, difficulties of living in Hong Kong, limited social interaction with others and local people's discriminatory behaviors. Those stressors were largely consistent with those summarized by a previous review of international students' difficulties studying abroad [21] and of local studies conducted among mainland students in Hong Kong universities [38][39][40].

Language Barriers and Local People's Discriminatory Behaviors
Among the stressors identified, language barriers and local people's discriminatory behaviors are commonly experienced by mainland students in Hong Kong [38][39][40]. We further added evidence that whether participants have language barriers depends on where they come from and their practical needs. Specifically, compared with students from northern and western China, students from the Guangdong province or neighboring provinces (e.g., Fujian) have low difficulty listening and speaking Cantonese. Parallel to the crosslinguistic similarity in foreign language learning [83], the similarities of participants' hometown dialect and Cantonese reduce their language obstacles. Additionally, whether the participants would perceive language as a barrier depends on the degree of their language proficiency and practical need in daily life. In an environment with the need to frequently interact with local people, such as discussions with supervisors and colleagues and fulfilling teaching assistance responsibilities, students with low Cantonese proficiency will have greater language difficulties.
Wang's qualitative study showed that perceived discrimination was not a significant stressor among mainland Chinese undergraduates in a Hong Kong university because they were not disturbed in their daily lives [44]. Compared with the younger undergraduate participants in Wang's study (n = 6), the PhD students in our study were expected to be more mature, autonomous, and politically concerned. They seemed to encounter more discrimination because of more interaction with local people and a greater likelihood of engaging in political debate or conflict. The tense political atmosphere during the social movement also exacerbated the discrimination towards mainland people to a higher level, which meant more possibilities of exposure to some local people's discriminatory behaviors.

Difficulties of Living in Hong Kong
In addition to the findings of Bhowmik's study about mainland Chinese students' difficulties living in Hong Kong (e.g., transport, food and accommodation) [40], we also revealed that subtle differences in climates due to the geographical locations of students' hometowns are also relevant. For example, the climate in southern China is more humid than in northern China, and the cooking style in southern China is blander than in northern China. Such differences in daily living might also impact these students' well-being. Therefore, future researchers and practitioners should consider the micro-level factors when examining academic sojourners' adaptation to another place.

Limited Social Interaction with Others
Limited social interaction with others was consistent with that reported by Yu and Zhang's study among 54 mainland students from four Hong Kong universities [38] and Wang's study among six mainland undergraduate students in a Hong Kong university [44]. In our study, we found that the interactional pattern among mainland students is affected by physical proximity. Similarly, as reported in Yu and Zhang's study, the interactional pattern among mainland students is strongly influenced by collectivism in the mainland educational system, such as "four to six classmates living in the same dormitory, attending the same lectures and eating in the canteen together" [38]. In both studies, "language barrier" [38] and "skills of cross-cultural communication with Hong Kong local students were not adequate" [44] are reported as important reasons for limited social interaction, but were mentioned less frequently in our study. Compared with undergraduate and postgraduate students, PhD students are required to be more independent and more devoted to their academic research, which shapes students' social interaction mode.

Differences in the Political Environment
The difference in the political environment is an important acculturative stressor. As indicated in Yu and Zhang's study [38], "Hong Kong is a highly politicalized city where opposing ideologies meet . . . One significant difference is the clashes of opposing political ideologies held by Hongkongers and Mainland students." A typical example is that some Hong Kong people use 'China' to refer to 'the mainland,' which could be regarded as improper by mainland students because it seems to indicate that Hong Kong people do not think Hong Kong is a part of China. Living in a socialist society and influenced by its educational/media system for years, mainland students may feel uncomfortable about such sayings. As reflected by one participant in our study, holding an explicit political view (i.e., acknowledging Hong Kong is part of China) is the premise to establish friendship between mainland students and Hong Kong students.
We found that our participants tended to avoid being involved in sensitive political topics, both in academic research and social life. For those participants who planned to return to the mainland to seek academic positions, they would actively avoid choosing supervisors whose research was on politically conflicting/sensitive areas to prevent the potential negative effect this may have on their future career path. For those who experienced the impact of the social movement in 2019, they would choose to avoid political expression to protect themselves from potential physical harm and discrimination because of the terrifying rumor. Evidence showed that the social movement harms the quality of life and well-being of Hong Kong people [84], whereas academic sojourners (e.g., mainland students in Hong Kong in 2019), as witnesses of this social movement, were also inevitably affected. Our findings revealed the special acculturative stressor that can be created at a certain time; we call for more research to explore how social environment (e.g., social events, social policy) and individual factors (e.g., career path, personal experience) may affect one's acculturation.

Implications
This study is one of the first studies to examine the adjustments among mainland Chinese PhD students studying in a different cultural setting, yet in the same country, from the perspective of the ELT Model. Our findings could help universities to identify the specific acculturative or academic needs among mainland Chinese PhD students in Hong Kong and provide recommendations for interventions to promote the improved academic and cultural adjustment of these students.
This study followed the dual transitions pointed out by the ELT model and enriched its application scenario to an intra-national context. On one hand, we remind future researchers to value both academic and acculturation transitions of international doctoral students when applying the ELT model in the cross-national context. On the other hand, our study adds new evidence to acculturation research that students who migrate for higher education within the same country also go through the process of acculturation, parallel to those who migrate between countries. Researchers should explore how the historical backgrounds of cities/states/provinces, the ways of living in hometowns (e.g., northern China vs. southern China) and social events/policy (e.g., the social movement in Hong Kong 2019) could bring subtle differences in people's acculturative experiences, as well as the roles of culture/individual characteristics in affecting students' academic experiences. Meanwhile, as China has long been the world's biggest source of international students [85], many Chinese students go abroad for higher education. We also call for more research caring about the well-being of mainland Chinese PhD students overseas, adding more evidence and informing the practice.
To reduce acculturative stressors, cross-cultural training (CCT) could be provided by local universities for new PhD enrollers from the mainland. CCT refers to formal educational efforts to help elicit affective, behavioral and cognitive changes for improving crosscultural adjustment and communication [86], which has been recommended for increasing students' confidence and ability to adjust effectively in a cross-cultural setting, raising their awareness towards the norms and ways of living in the host society [87]. It may also be advised for universities to provide pre-departure online CCT to new mainland students [88]. Reliable information resources (e.g., online living guidance brochure, links for helping cultural adaption, brief introduction of services provided by universities) could be provided alongside the admission notice. After students' arrival, CCT could be organized through seminars and workshops for new mainland students in Hong Kong [89]. In addition, having local and non-local students engage together in purposeful cross-cultural interaction may facilitate those students' successful adjustment to the new learning and living environment [90]. Students are also encouraged to attend Cantonese learning classes to improve their language proficiency.
To reduce academic stressors, more support from the supervisors, the departments and the universities should be provided in the academic environment. For students who lack academic guidance on their research or suffer from a poor supervisory-student relationship (SSR), universities should establish formal regulations to guarantee academic interaction between supervisors and students. For example, detailed provisions on the frequency of meeting and communicating [91] and regular meetings can also cover content that improves students' critical thinking and problem-solving methods [92]. Meanwhile, supervisors also need professional guidance for establishing good relationships with their students. Faculty may consider organizing regular cases-based workshops or professional development activities to support supervisors to build a good SSR [93]. Universities may also arrange term feedback from students to assess the quality of the SSR and the effectiveness of the supervisor's guidance [94,95] and to assess whether an improvement or termination of the SSR should be made. In addition, experiences and lessons could also be summarized from mutual feedback for the future workshop's use. Lastly, universities may use social network sites (e.g., Facebook, Instagram, WeChat) to promote mental health awareness [96], establish meaningful social connections [97] among PhD students and, eventually, improve their academic experience. Specifically, tips for the PhD jour-ney, interaction zone and online emotional assistance could be embedded in existing social network platforms, the university's exclusive applet or the official website to give social support to help students avoid a poor SSR, which could also enlarge students' social interaction, help them find those with similar experience to themselves and enhance their psychological well-being.
For students who change their major or research direction, more emotional support, professional support [98] and timely feedback from departments and supervisors should be provided during their academic transition to help students establish confidence and skills when facing difficulties. For students who have problems establishing self-discipline and independence in their research, the department and supervisors may help them find the barriers, set goals of fostering self-discipline and create a climate that is supportive of a self-discipline emphasis [99]. For those experiencing uncertainties about their career paths, faculty may consider organizing job counseling workshops or seminars, inviting alumni from different career paths to share their experiences in a group format and providing informational support on job searching, interviewing skills or workplace behavior to current students [100].

Limitations
This study had limitations. Firstly, the use of purposive sampling as a non-probability sampling method may lead to a degree of selection bias in the recruitment [101]. In particular, the interviewees' availability and willingness to participate are also important during recruitment [102]. Therefore, we may have missed some cases with other transition stressors or without any negative experiences. Considering this, the generalizability of the findings should not be exaggerated. Secondly, we observed that some participants avoided sharing their negative experiences or feelings in front of strangers due to social desirability bias [103]. Thirdly, we only included PhD students in our interviews; the inclusion of staff from universities, faculties and supervisors may provide a more comprehensive view and enhance the practical significance, for example, to explore the gaps between students' needs and the existing services that have been provided. Further research may consider adopting the triangulation method to increase the credibility and validity of the research findings [104], using individual in-depth interviews or follow-up interviews [105]. Finally, it should be noted that this study was conducted during COVID-19 with different pandemic-control policies in place. A prior study has found that social distancing measures during the COVID-19 pandemic may delay students' research progress [106], which may heighten students' stress regarding their academic experiences. Those external factors might bring additional negative impacts on the academic/acculturative stressors experienced by the students.

Conclusions
Adjustment outcomes among mainland Chinese PhD students in Hong Kong should receive more empirical attention. Guided by the ELT Model, our findings identified specific academic stressors and acculturative stressors among mainland Chinese PhD students in Hong Kong. Theoretically, we extend the application scenario of the ELT model to the Asian context and within the same country (i.e., mainland China and Hong Kong); we also first adopt a comprehensive view of the education and life transitions of doctoral students in the cross-cultural setting.
For academic stressors, high expectations from the supervisor, emphasis on self-discipline as PhD students, peer comparison in academia and uncertainties about future careers were similar to those reported by previous studies among PhD students in mainland China and overseas. However, difficulties in changing discipline/research direction were identified as a special stressor in this study, which should not be ignored by the relevant scholars and practitioners. Moreover, financial concern was not a significant stressor in our study, which indicated that, as an important part of higher education, doctoral training systems vary in different countries/regions. For acculturative stressors, the common stressors-namely language barriers, local people's discriminatory behaviors, differences in the political environment, limited social interaction with others and difficulties of living in Hong Kong (e.g., accommodation) -basically overlap with those reported by previous local studies. Meanwhile, we added new evidence that the subtle differences (i.e., climate, food) caused by the different geographical regions also affect their adaptation. In addition, we gave a special spotlight to the social event, i.e., the social movement in Hong Kong in 2019; this typical example of the difference in the political environment poses challenges to students' acculturation.
Practically, to better address those students' academic and acculturative stressors, appropriate interventions (e.g., cross-cultural training), as well as support from the supervisors, the departments and the universities, should be provided. For future research, scholars should value both academic and acculturation transitions of international doctoral students in the cross-national education journey and their well-being. Researchers need to pay attention to exploring how the historical backgrounds of cities/states/provinces, the ways of living in hometowns and social events/policies could bring subtle differences in people's acculturative experiences, as well as the roles of culture/individual characteristics in affecting students' academic experiences.
Supplementary Materials: The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/ijerph20126078/s1, Table S1: Focus group interview questions; Table S2: Themes and subthemes from the focus group interview; Figure   Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.

Data Availability Statement:
The data presented in this study are available on reasonable request for academic use from the corresponding author after anonymization. The data are not publicly available to ensure the participants' confidentiality.